The　safety　of　on-fire　trains　moving　in　subway　tunnel　is　important　to　emergency　rescue,　and　the　train　velocity　is　the　key　to　the　train　safety.　This　paper　adopts　a　fire　prototype　with　a　heat　release　rate　of　0~10MW　to　perform　a　model　experiment　of　train　fire　in　a　1:8　subway　tunnel　model.　After　a　similar　transformation,　the　heat　release　rate　of　the　model　fire　reaches　0~55kW.　By　using　n-heptane　as　the　fuel　and　by　adopting　a　frequency　conversion　fan　to　form　a　flow　field,　the　motion　of　the　train　in　the　model　tunnel　is　simulated,　and　the　relationship　between　the　wind　velocity　and　the　heat　release　rate,　the　temperature　field　around　the　train　and　the　flame/smoke　pervasion　rule　are　investigated　in　the　conditions　of　variable　train　velocity,　fire　location　and　fire　source　location.　Finally,　by　taking　Beijing　Metro　for　example,　the　most　suitable　velocity　of　on-fire　train　in　subway　tunnel　is　estimated　as　41.83km/h.